This application relates to a refrigerant system having a variety of operational features. In particular, a reheat coil is incorporated and can selectively receive a refrigerant flow from a location either upstream or downstream of a condenser to provide precise control over system operation characteristics. In further features, an economizer circuit is incorporated into the system, to selectively function in conjunction with the reheat coil, as well as the ability to bypass the condenser is provided.
This application relates to refrigerant systems that incorporate both an economizer cycle concept and a reheat coil to provide better dehumidification performance and temperature control in response to variable latent and sensible heat load demands.
Refrigerant systems are utilized to control the temperature and humidity of air in various environments. In a typical refrigerant cycle, a refrigerant is compressed in a compressor and delivered to a condenser. In the condenser, heat is exchanged between outside ambient air and the refrigerant. From the condenser, the refrigerant passes to an expansion device, at which the refrigerant is expanded to a lower pressure and temperature, and then to an evaporator. In the evaporator heat is exchanged between the refrigerant and the indoor air, to condition the indoor air. When the refrigerant system is operating in a cooling mode, the evaporator cools the air that is being supplied to the indoor environment.
In addition, as the temperature of the indoor air is lowered, moisture usually is also taken out of the air. In this manner, the humidity level of the indoor air can also be controlled.
In some cases, the temperature level, to which the air is brought to provide a comfort environment in a conditioned space, may need to be higher than the temperature that would provide the ideal humidity level. This has presented design challenges to refrigerant system designers. One way to address such challenges is to utilize reheat coils. In many cases, the reheat coils, placed in the way of indoor air stream behind the evaporator, are employed for the purpose of reheating at least a portion of the air supplied to the conditioned space after it has been overcooled in the evaporator, where the moisture has been removed.
On the other hand, enhancement of system efficiency is one of the foremost concerns in the HVAC&R industry. One of the options available to the refrigerant system designer to increase efficiency is a so-called economizer cycle. In the economizer cycle, a portion of the refrigerant flowing from the condenser is tapped and passed through an economizer expansion device and then to an economizer heat exchanger. This tapped refrigerant subcools a main refrigerant flow that also passes through the economizer heat exchanger. The tapped refrigerant leaves the economizer heat exchanger usually in a vapor state and is injected back into the compressor at an intermediate compression point. The subcooled main refrigerant is additionally subcooled after passing through the economizer heat exchanger. Then the main refrigerant flows through a main expansion device and to the evaporator. This main refrigerant flow will provide a higher capacity and/or efficiency, due to extra subcooling in the economizer heat exchanger. An economizer cycle thus provides enhanced system performance characteristics.
As mentioned above, another option available to a refrigerant system designer is to include a reheat coil into the system schematics. As known, at least a portion of the refrigerant upstream of the expansion device is passed through a reheat heat exchanger and then is returned back to the main circuit. At least a portion of a conditioned air, having passed over the evaporator, is then passed over this reheat heat exchanger to be reheated to a desired temperature.
Recently, the assignee of this invention obtained a patent disclosing the use of both a reheat coil and an economizer cycle in a refrigerant system. Still various schematics can provide enhanced control over such systems as well as flexibility in their design and operation.